Multiple sclerosis (MS) is an inflammatory disease of the nervous system where the fatty myelin sheaths around the axons of the brain and spinal column are damaged. As a result of this damage, the ability of nerve cells in the brain and spinal cord to communicate with each other is compromised. Almost any neurological symptom, including physical and cognitive disability, can appear with the disease. MS affects more than 350,000 people in the United States and 2.5 million worldwide. In the United States, prevalence estimates are approximately 90 per 100,000 people.
Beginning with the first description of the anatomy associated with MS by Jean-Martin Charcot in 1868, MS plaques associated with MS have been known to be centered or located around veins. Further, it has been recently shown that MS is significantly correlated with a condition called chronic cerebrospinal venous insufficiency (CCSVI). CCSVI is a condition where people have obstructed blood flow in the veins that drain the central nervous system (the brain and spinal cord) and is characterized by multiple stenoses of the principal pathways of extracranial venous drainage, the internal jugular veins (IJV) and the azygous veins (AZV), with opening of collaterals, clearly demonstrated by means of selective venography and magnetic resonance venography (MRV).
Stenosis literally means a “narrowing.” Here “stenosis” or its plural “stenoses” is an abnormal narrowing of the vein that restricts blood flow. This abnormal narrowing may be the result of many things. For example, the abnormal narrowing maybe the result of a collapse of the vein, twisting of the vein, ring-like narrowings in the vein and other similar obstructions. Further, the abnormal narrowing may be the result of severe venous problems including veins that are partially closed, underdeveloped, minimally formed or almost entirely missing. In addition, an abnormal or defective valve, septum, flap or membrane may narrow, blocks or inhibit blood flow through the veins. Finally, the build up of plaque, fibrin or thrombus may cause an abnormal narrowing of the vein. With respect to MS, a consequence of a stenosis in a vein leads to problems with normal or efficient blood drainage from the brain and spine back to the heart.
Intravascular ultrasound (“IVUS”) combined with a technique called virtual histology (“VH”) has been particularly successful in recognizing the morphology of atherosclerotic plaque in vivo (i.e., the location and composition of plaque in the patient's body). Current developments are underway to also be able to recognize thrombus in vivo. FIG. 1 illustrates a typical intravascular imaging system 2 that uses intravascular ultrasound (IVUS). FIG. 2 illustrates a typical intravascular imaging system 2 that uses optical coherence imaging (OCT).
An example of an IVUS system is the s5i™ Imaging System sold by Volcano Corporation of San Diego, Calif. Examples of OCT imaging systems include, but are not limited to, those disclosed in U.S. Pat. No. 5,724,978 issued Mar. 10, 1998 entitled “Enhanced accuracy of three-dimensional intraluminal ultrasound (ILUS) image reconstruction” with Harm Tenhoff as inventor, US Published Patent Application Nos. 20070106155 entitled “System and method for reducing angular geometric distortion in an imaging device” with John W. Goodnow and Paul Magnin as inventors and published on May 10, 2007, 20080287801 entitled “IMAGING DEVICE IMAGING SYSTEM AND METHODS OF IMAGING” with Russell W Bowden, Tse Chen Fong, John W. Goodnow, Paul Magnin and David G. Miller and published on Nov. 20, 2008, 20090093980 entitled “REAL TIME SD-OCT WITH DISTRIBUTED ACQUISITION AND PROCESSING” with Nathanial J. Kemp, Austin Broderick McElroy and Joseph P. Piercy as inventors and published on Apr. 9, 2009, 20080119701 entitled “ANALYTE SENSOR METHOD AND APPARATUS” with Paul Castella, Nathaniel J. Kemp and Thomas E. Milner as inventors and published on May 22, 2008, 20090018393 entitled “CATHETER FOR IN VIVO IMAGING” with Larry Dick, Thomas E. Milner and Daniel D. Sims as inventors and published on Jan. 15, 2009, 20090046295 entitled “APPARATUS AND METHODS FOR UNIFORM SAMPLE CLOCKING” issued to Nathaniel J. Kemp, Roman Kuranov, Austin Broderick McElroy and Thomas E. Milner as inventors and published on Feb. 19, 2009, 20090284749 entitled “OCT Combining Probes and Integrated Systems” with Dale C. Flanders and Bartley C. Johnson as inventors and published on Nov. 19, 2009 and WIPO Published Patent Application No. WO2009023635 entitled “FORWARD-IMAGING OPTICAL COHERENCE TOMOGRAPHY (OCT) SYSTEMS AND PROBE” with Jonathan C. Condit, Kumar Karthik, Nathaniel J. Kemp, Thomas E. Milner and Xiaojing Zhang as inventors and published on Feb. 19, 2009, the collective teachings of which, in their entirety, are incorporated herein by reference.
Such imaging systems 2 may also include systems capable of identifying the makeup of the tissue and material of a patient's vasculature including so called virtual histology (VH) systems. An example of a VH system is the s5i™ Imaging System with VH capability sold by Volcano Corporation of San Diego, Calif. The imaging systems 2 may also include systems for measuring the flow of blood in a patient's vasculature. An example of such a blood flow measurement system is a color-Doppler ultrasound imaging system sold under the brand name of Chromaflow® by Volcano Corporation of San Diego Calif.
In an exemplary imaging system 2, an intra-vascular ultrasound (IVUS) console 4 is electrically connected to an IVUS catheter 6 and used to acquire RF backscattered data (i.e., IVUS data) from a blood vessel. The IVUS console 4 typically includes a computing device 8 comprising a database 10 and a characterization application 12 electrically connected to the database 10 and adapted to receive IVUS data from the IVUS console 4 or directly from a transducer 14. Specifically, a transducer 14 is attached to the end of the catheter 6 and is carefully maneuvered through a patient's arteries to a point of interest along the artery. The transducer is then pulsed to acquire high-frequency sonic echoes or backscattered signals reflected from the tissue of the vascular object. Because different types and densities of tissue absorb and reflect the ultrasound pulse differently, the reflected data (i.e., IVUS data) is used to image the vascular object. In other words, the IVUS data can be used (e.g., by the IVUS console 4 or a separate computing device 8) to create an IVUS image.
An exemplary IVUS image 16 is shown in FIG. 2, where the light and dark regions indicate different tissue types and/or densities. It should be appreciated that the IVUS console 4 depicted herein is not limited to any particular type of IVUS console, and includes all ultrasonic devices known to those skilled in the art (e.g., a Revolution® or EagleEye® IVUS catheter used in conjunction with an s5i™ IVUS imaging system, all of which are sold by Volcano Corporation of San Diego, Calif.). It should further be appreciated that the IVUS catheter 6 depicted herein is not limited to any particular type of catheter, and includes all ultrasonic catheters known to those skilled in the art. Thus, for example, a catheter having a single transducer (e.g., adapted for rotation) or an array of transducers (e.g., circumferentially positioned around the catheter or longitudinally along the catheter 6) can be used with the typical imaging system 2.
It should be appreciated that the database 10 depicted herein includes, but is not limited to, RAM, cache memory, flash memory, magnetic disks, optical disks, removable disks, SCSI disks, IDE hard drives, tape drives and all other types of data storage devices (and combinations thereof, such as RAID devices) generally known to those skilled in the art. It should further be appreciated that the characterization application 12, as depicted and discussed herein, may exist as a single application or as multiple applications, locally and/or remotely stored. It should also be appreciated that the number and location of the components depicted in FIG. 1 do not limit a typical imaging system 2 but are merely provided to illustrate a typical imaging system 2. Thus, for example, a computing device 8 having a plurality of databases 10 or a remotely located characterization application 12 (either in part or in whole) or any combination of these may also be found in a typical imaging system 2.
In one embodiment of a typical imaging system 2, the characterization application 12 is adapted to receive and store characterization data (e.g., tissue type, etc.). The characterization data was determined prior to using the tissue—characterization system 2 as follows. After a specimen vascular object has been interrogated (e.g., IVUS data has been collected), a histology correlation is prepared. In other words, the specimen vascular object is dissected or cross-sectioned for histology. In one method of producing characterization data, the cross-section is previously marked, for example with a suture, so that the histology can be corresponded to a portion of the IVUS image. The cross-section is then prepared with a fixing and staining process that is well known in the art. The staining process allows a clinician to identify a tissue type(s), or a chemical(s) found within (e.g., a chemical corresponding to a particular tissue type, etc.). The identified tissue type or types is then correlated to the IVUS data as will be explained below.
Where the imaging system 2 is or includes an OCT system, the imaging system 2 typically includes a light source 20 that produces light of a desired frequency and with other desired characteristics well understood in the art that is ultimately directed from the catheter 6 to the patient's vasculature by distal optics 22. A typical OCT imaging system 2 has the light source 20 located remotely from or nearby the catheter 6. Optical fibers 24 carry the light from the light source 20 to the distal optics 22.
It should be appreciated that there may be many methods used to identify or characterize the cross-sectional object as is well understood in the art besides the method just described. Thus, any identification/characterization method generally known to those skilled in the art may be used to characterize tissue. The identified tissue type or characterization (i.e., characterization data) is then provided to the characterization application 12. In one embodiment, as shown in FIG. 1, the characterization data is provided via an input device 18 electrically connected to the computing device 8. The characterization data is preferably then stored in the database 10. It should be appreciated that the input device depicted herein includes, but is not limited to, a keyboard, a mouse, a scanner and all other data-gathering and/or data-entry devices generally known to those skilled in the art. It should further be appreciated that the term tissue type or characterization, as these terms are used herein, include, but are not limited to, fibrous tissues, fibro-lipidic tissues, calcified necrotic tissues, necrotic core, calcific tissues, collagen compositions, cholesterol, thrombus, compositional structures (e.g., the lumen, the vessel wall, the medial-adventitial boundary, etc.) and all other identifiable characteristics generally known to those skilled in the art.
In one method of characterizing tissue, the characterization application is adapted to create a histology image and to identify at least one corresponding region on an IVUS image. Specifically, digitized data is provided to the characterization application (e.g., via the input device 18), where the digitized data corresponds to the cross-sectioned vascular object. The digitized data is then used to create a histology image (i.e., a digital image or outline that substantially corresponds to the vascular object). A region of interest (ROI) on the histology image can then be identified by the operator. Preferably, the ROI is characterized by the characterization data, as previously provided, and may be the entire histology image or a portion thereof. The characterization application is then adapted to identify a corresponding region (e.g., x,y coordinates, etc.) on the IVUS image.
In view of the foregoing, what is needed is an effective method and device for assisting a healthcare provider to identify patients whose MS, or MS symptoms, are likely exacerbated if not caused, at least in part, by blockages of one or more of the patient's internal jugular veins (IJV) or azygous veins (AZV) and for those patients, methods and devices for applying one or more therapies to the blockages in the patient's IJV or AZV veins.